The ongoing collaborative US-USSR study of the prevalence of dyslipoproteinemias, based on the Lipid Research Clinics Study protocol, is described. The purpose of this multidisciplinary, multiclinic program is to investigate the relation of plasma lipids and lipoproteins and other risk factors to atherosclerotic disease in selected populations. The research design, sampling strategy and general hypotheses of the study are detailed. Common quality control methods and standardized screening procedures used in data collection are reviewed. Components of the study include measurement of plasma lipids and lipoproteins, the collection of demographic and physiologic information, a 24-hour dietary recall, administration of the Rose questionnaire and resting and exercise electrocardiograms. Preliminary comparative data for total plasma cholesterol, triglycerides and high density lipoprotein cholesterol are presented for men aged 40 to 59 years.